A track type machine utilizes chains on either side of the machine that are connected to ground engaging elements known as shoes to move the machine. Specifically, a sprocket driven by an engine of the machine engages links of the chain to translate the chain about spaced apart pulley mechanisms. As the chain translates about the pulley mechanisms, the connected shoes engage a work surface under the machine to transmit torque from the sprocket to the surface in a direction opposite the desired travel direction of the machine, thereby propelling the machine. Depending on the weight of the machine, size of the chain, degrading environment in which the machine is operating, and other similar factors, the chains and/or shoes may wear or be damaged and require periodic inspection, servicing, repair, and/or replacement.
Typically, a master link is provided in the chain to allow disassembly of the chain (i.e., separation of two ends of the chain). The master link is available in many forms, but generally includes four half links (two half links per side), each of the half links receiving either a bushing or a pin. After the bushing and pin have been inserted into the half links, a flat upper surface of each half link abuts a flat lower surface of the shoe, and the entire assembly is bolted together with fasteners extending from an outer surface of the shoe into threaded holes within each half link. Although this type of joint has been successfully utilized on track type machines in the past, it suffers from durability problems. Specifically, the fasteners have been known to break or the threads within the half links have been known to strip. In these situations, the links of the chain may separate, leaving the machine stranded. Additionally, when the threads strip, the entire half link must be replaced. It is also possible, given the flat clamping surfaces of the shoe and half links, for the shoe to translate relative to the half links, requiring adjustment and/or replacement of the links and shoes.
An improved master link design is disclosed in U.S. Pat. No. 4,083,611 (the '611 patent) issued to Shaffner et al. on Apr. 11, 1978. In the '611 patent, Shaffner et al. describes and illustrates a master link assembly for a crawler tractor that comprises two laterally spaced apart (left and right) parallel master links. Each of the master links comprises two overlapping half links held in alignment by a pin extending into registering pin holes in the half links. The overlapping half links are mechanically secured together in fixed relationship by cap screws, which extend through holes in a track shoe that overlies both half links. The cap screws thread into tapped holes in the half links. Besides aligning the overlapping half links, each pin also serves as a safety connection in case the cap screws break, and also enables removal of the cap screws and replacement of the track shoe without breaking the track assembly. Axial displacement of a pin from its pin holes is prevented by arranging at least one tapped screw hole in each half link so that a cap screw, when fully inserted therein, engages a groove in the side of the pin and prevents axial movement of the pin out of the half link holes.
Although the improved master link design of the '611 patent may address some of the durability problems described above, the design has certain limitations. In particular, the half links and shoe of the '611 patent still abut along a generally planar surface. A planar abutment may be prone to misalignment during assembly and slippage during machine operation. In addition, because the cap screws still connect to threaded holes in the half links, when the threads strip, the half links must still be replaced, which can be an expensive and time consuming process.
The disclosed master link design is directed to overcoming one or more of the problems set forth above.